Helminths are parasitic worms classified into three main groups—nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes)—based on their body structure, life cycle, and mode of infection. This classification helps in understanding their biology, disease-causing potential, and guides accurate diagnosis, treatment, and control strategies.

1. Classification of helminthes:
intestinal nematodes 1
Dr. Omokhua G.I
University of Benin
23th July 2025

2. Outline
• Classes of helminthes
• Mode of transmission
• Laboratory diagnosis
• Treatment
• Prevention and control

3. Classification of Helminths
a. Nematodes
• Intestinal nematodes:
• Small intestine: Ascaris lumbricoides,Ancylostoma duodenale, Necator
americanus, Strongyloides stercoralis, Trichinella spiralis
• Large intestine: Enterobius vermicularis, Trichuris trichuria
• Blood/Tissue nematodes:
• Lymphatics: Wuchereria bancrofti, Brugia malayi, Brugia timori
• Subcutaneous: Onchocerca volvulus, Mansonella streptocerca,
Dracunculus medinensis
• Conjunctiva: Loa loa
• Body cavity: Mansonella perstans, Mansonella ozzardi

4. Classification of Helminths
b. Platyhelminthes
• Cestodes
• Taenia solium, Taenia saginata, hymenolepsis nana, diphylobothrium
lactum, Echinococcus granulosus, Echinococcus multicularis
• Trematodes
• Blood trematodes: vesicalvenous plexus-Schistosoma haematobium;
rectal /portal venous plexus-S. mansoni, S. japonicum
• Hepatic trematodes: Fasciola hepatica, Clonorchis sinensis, Opisthorchis
felineus
• Lung trematodes: Paragonimus westermani
• Intestinal trematodes: Fasciolopsis buski, Heterophyes heterophyes

5. Nematodes (Roundworms)
• Cylindrical, unsegmented body, enlongated
• Complete digestive tract
• Dioecious
• Body cavity-Pseudocoelomate
• Lack sucker and hooks
• Complete their life cycle in one host except the filarial and guinea
worms
• Infection transmission: ingestion of eggs or encysted larva stage, larva
penetration thru surfaces and insect vectors

6. Cestodes (Tapeworms)
• Flat and have ribbon like chains of segments (proglottids)
• lack digestive tract
• Monoecious-Hermaphroditic
• Lack body cavity-Acoelomate
• Have sucker often with hooks
• Complete their life cycle in one (H.nana) or more than one host (others)
• Most of the cestodes, humans are the definitive host except E. granulosus
• Taenia solium humans may act as the definitive and intermediate host
• Infection transmission: ingestion of undercooked meat/fish containing the
encysted larvae or eggs

7. Trematodes (Flukes)
• leaf-like body, unsegmented
• Incomplete digestive tract
• Mostly hermaphroditic (monoecious) except for Schistosomes
• Lack body cavity-Acoelomate
• Have sucker, no hooks
• Complete their life cycle in one definitive host (man) and two intermediate
host: fresh water snail (1st
) and fresh water fish, crustanceans or aquatic
plants (2nd
)
• Infection transmission: ingestion of metacercariae or skin penetration by the
cerceriae

8. Modes of Transmission
• 1. Fecal-oral route
• 2. Skin penetration
• 3. Vector-borne
• 4. Ingestion of raw or undercooked meat/fish

9. Risk Factors
• Poor sanitation and hygiene
• Walking barefoot in contaminated area
• Consuming raw or undercooked food
• Drinking contaminated water
• Tropical and subtropical endemic regions
• Children
• farmers

10. Prevention and Control
• Hand washing
• Provision of clean water
• Proper cooking
• Wearing shoes
• Regular deworming programs
• Vector control (nets, sprays)
• Avoid contact with contaminated freshwater

11. Practice exercise
• Classify helminthes of medical importance
• Differentiate between nematodes, cestodes and trematodes based on
their shapes, sexes, alimentary canal, body cavity and mode of
infection transmission
• Discuss the mode of transmission of helminthic infections with
examples
• Discuss the risk factors of helminthiasis
• Discuss the prevention and control of helminthiasis